Circuit for rapid excitation and de-excitation of an electromagnetic switch

ABSTRACT

For rapid excitation and de-excitation of electromagnetic switches, such as relays, contactors, magnetic valves, and the like, the excitation winding of an electromagnetic switch is passed by a steady holding direct current via a choke connected in series therewith. The holding current is adequate for holding the armature when the armature is pulled up, but is inadequate for pulling up the armature from its rest position. A first series circuit arrangement connected in parallel with the series connection of the excitation winding and the choke comprises a first controllable semiconductor switch and a first capacitor. A second series circuit arrangement connected in parallel with the excitation winding comprises a second controllable semiconductor switch and a second capacitor. The first series circuit arrangement produces a pulse-like current amplification of the holding current in the excitation winding when its semiconductor switch is controlled. The second series circuit arrangement produces a pulse-like current reduction of the holding current in the excitation winding when its semiconductor switch is controlled.

United States. Patent Hoffmann et al.

[54] CIRCUIT FORRAPID EXCITATION AND DE-EXCITATION OF AN ELECTROMAGNETIC SWITCH [72] Inventors: Manired lloffmann, Erlangen; Peter Schulze, Utte'nreuth, both of Germany [73] Assignee: Siemens Aktiengesellschaft, Berlin and Munich, Germany [22] Filed: Dec. 13, 1971 2i] 'Appl.No.: 207,004

[30] Foreign Application Priority Data Dec. 18, 1970 Germany ..P 20 62 387.4

[52] US. Cl. ..317/151, 317/148.5 B, 317/157,

317/DlG. 4, 317/DIG. 6

[51] Int. CL... ..'...H01h 47/22 [58] Field of Search ..317/151, DIG. 6,

. DIG. 4, 148.5 R,3l7/l48.5'B 157;

[56] i 7 References Cited UNITED STATES PATENTS "3,374,422 3/1968 Blume ..317/148.5B

[15 1 3,702,425 [451 Nov.7, 1972 Primary Examiner l. D. Miller Assistant Examiner-Harry E. Moose, Jr. Attorney-Arthur Wilfond et al.

[57] ABSTRACT For rapid excitation and de-excitation of electromagnetic switches, such as relays, contactors, magnetic valves, and the like, the excitation winding of an electromagnetic switch is passed by a steady holding direct current via a choke connected in series therewith. The holding current is adequate for holding the armature when the armature is pulled up, but is inadequate for pulling up the armature from its rest position. A first series circuit arrangement connected in parallel with the series connection of the excitation winding and the choke comprises a first controllable semiconductor switch and a first capacitor. A second series circuit arrangement connected in parallel with the excitation winding comprises a second controllable semiconductor switch and a second capacitor. The first series cirwit a aq P d s .Pl lssi ikq ltml tatn: plification of tfie holding .current in the excitation winding when its semiconductor switch is controlled.

The second series circuit arrangement produces a pulse-like current reduction of the holding current in the excitation winding when its semiconductor switch is controlled.

10 Claims, 1 Drawing Figure la. o

CIRCUIT FOR RAPID EXCITATION AND DE- EXCITATION OF AN ELECTROMAGNETIC SWITCH v .The presentinvention relates to a'circuit for rapid excitation and de-excitation of an electromagnetic switch.

In magnetically controllable switches such as, for'example, relays, contactors, magnetic valves, and the like, an excitation winding is energized with direct current or with rectified alternating current thereby. producing a'magnetic field in the magnetic circuit which pulls up an armature of magnetizable work material. As a result of the pull-up of the armature, the

operating contacts can be closed or the break contacts can be opened. In magnetic valves, airof moisture is either released or blocked as a result of the pull-up of the armature.

ln magnetic switches of this type, the consumption of excitation current and the excitation time depend on the armature load and the travel distance of the armature. Hence, a switch ON command is provided only following a typical delay period.

The de-excitation of such magnetic switches also entails afdelay period, since, during the de-excitation'of the excitation winding, the magnetic field must first be removed until the armature is de-energized.

A decrease of the delay periodduring the excitation or the de-excitation of magneticswitches necessitates special mechanical and/or electrical measures which are expensive. Such measures are, for example, the use of several windings, possibly comprising a plurality of windings. v

An object of the invention is to provide a circuitfor rapid excitation and de-excitation of an electromagnetic switch utilizinga single and simple winding.

Another object of the invention is to provide a circuit for rapid excitation and-de-excitation of an electromagnetic switch of simple structure which functions with efficiency, effectiveness and reliability.

s Still another object of the invention is to providea circuit for rapid excitationand de-excitation of electromagnetic switches such as relays, contactors, magnetic valves, and the like, utilizing direct current, or rectified alternating current.

In accordance with the invention, the excitationwinding of the switch is passed by a steady holding current via a choke connected in series with the excitation winding. The holding current is adequate for holding the armature when the armature is pulled up, but not for pulling-up the armature from its rest position. A"

first series circuit arrangement connected parallel to the series connection of the excitationwinding and the choke comprises a first controllable semiconductor switch and a first capacitor. A second series circuit arrangement connected parallel to the excitation comprises a second-controllable semiconductor switch and a second capacitor. The first circuit arrangement" produces a pulse-like current amplification of the hold 4 ing current in the excitation winding when the first semiconductor switch is controlled. The second circuit produces a pulse-like current reduction of theholding current in the excitation winding when the second semiconductor switch is controlled.

One diode, poled in forward direction, is connected into the holdingcircuit of the excitation winding ahead of the choke and another diode, poled in forward direction, is connected behind the excitation winding.

2 v A third diode is connected in shunt with the choke and is poled in inverse direction for the holding current of the excitation winding.

Each of the fust and second series circuit arrangements comprises a capacitorconnected in series with a circuit arrangement is coupledto the positive terminal of the source of voltage and the capacitor of the first series circuit arrangement is connected to the negative terminal of the source of voltage. The second series circuit arrangement switches off the electromagnetic switch. The'thyristor of the second series circuit arrangement is connected to the negative terminal of the sources of voltage and the capacitor of the second series circuit arrangementhis connected tov a common point in the connection between the choke and the excitation winding.

The thyristor of each of the first and second series circuit arrangements has a control electrode. The thyristor of the first series circuit arrangement is con- .trolled by a control signal supplied thereto to release the switch On condition of the electromagnetic switch. The thyristor of the second series circuit arrangement is controlled by a control signalsupplied thereto to release the switch OFF condition of the electromagnetic switch.

The choke has an inductivity at leastequal to the inductivity of the excitation winding of the switch.

The electromagnetic switch has a magnetic circuit comprising laminated sheets.

border that the invention may be readily carried into effect, it will now be described with reference'to the accompanying drawings, wherein the single FIGURE is a circuit diagram of an embodiment of the circuit of the invention for rapid excitation and de-excitation of an electromagnetic switch.

Inthe Figure,-a rectifier device G is connected to an AC current source U and comprises rectifiers G I in bridge connection, and a charge capacitor C connected to the-output of the rectifier bridge. The rectified and smoothed DC supply current flows from thepositive terminal 1 of the rectifier device G via a diode n5, poled in forward direction, and a choke k2 through the excitation winding k1 of the magnetic switch and via a diode n1, poled in forward direction, to the negative prising a first thyristor n3 connected in seriescircuit ar- I rangement with a first capacitor k3 is connected parallel to the terminals 1 and 2 of the rectifier device G and parallel to the series connection of the choke k2 and the excitation winding k1, including the diode n1. One of the plates of the capacitor k3 is connected to the terminal 2 of the rectifier device G.

A second series circuit arrangement comprising a second thyristor n4 connected in series circuit arrangeresults from the firing of ment with a second capacitor k4 is connected parallel to the excitation winding k1 of the magnetic switch and parallel, to'the excitation winding kl and the diode n1. One of the plates of the capacitor k4 is connected to a common point in the connection between the chokekl and the excitation winding k It is assumed that the armature switch is in its rest position, meaning in its dropped-out condition, when the current is the steady holding current I If the armature is then to be pulled up, the thyristor n3 is fired by a control signal supplied to its control electrode. Thus,'the excitation winding k1 of the magnetic switch is'superexcited by the discharge current of the first capacitor k3.

The amplitude and duration of the pulse current l of the magnetic may be so adjusted ,by the selection of the magnitude of the capacitance of the first capacitor k3 and of the capacitor voltage U that the armature of the magnetic switch will pull up with certainty and will remain pulled up after the decay of the excitation surge or pulse. The amplitude of the switch ON current surge must be determined according to the armature air gap in the magnetic circuit of the switch and according to the counter force'of the armature (a release spring for example) and should correspond to a multiple value of theholding current I The magnetic switch is disconnected by the second thyristor n4. When the second thyristor n4 is fired via its control path, the excitation winding kl of the magnetic switch is quickly excited. The holding current 1,,

with an initial current steepness dI /dt U,,,/ (1.) is

rendered zero during the discharge of the second capacitor k4. The discharge of the second capacitor k4 the second thyristor n4 if the current in the choke k2 undergoes only very slight changes. The excitation winding k1 of the magnetic switch remains currentless until the second capacitor k4 is discharged via the choke k2. The annature of the magnetic switchmay drop out during this time, which should last five to ten times longer than the excitation time. The inductivity of the excitation winding k1 and the inductivity of the choke k2 and the capacitances of the first and second capacitors k3 and k4may be provided in such magnitudes as to permit the switch OFF or disconnectionof the magnetic switch, even during the switch ON process. To accomplish this, the inductivity of the choke k2 should be selected to be as high as, or preferably even higher than, the inductivity of the excitation winding k1. If the voltage U of the second capacitor k4 is approximately two times the voltage of the first capacitor k3, or 2 U thenthe capacitance of said second capacitor should be at least twice the magnitude of the capacitance of said first capacitor.

The electromagnet switch has a magnetic circuit which preferably comprises laminated sheets, since otherwise, rapid deexcitation will not be effective due to existing eddy currents. I

. While the invention has been described by means or,

a specific example and in a specific embodiment, we do not wish to be limited thereto, for obvious modifications will occur to those skilled in the art without departing from the spirit and scope of the invention.

We claim: j I

l. A circuit for rapid excitation and de-excitation of an electromagnetic switch such as a relay, contactor,

means.

series circuit arrangement switches netic switch and the thyristor of the first series circuit magnetic valve, and the like, by direct current, the electromagnetic switch hav'ng an excitation winding and an armature controlled in position by the excitation winding, said. circuit comprising a choke connected in series with the excitation winding; current supply means coupled to the choke and the excitation winding for providing aflow of steady holding current through the excitation winding viathe choke, the current having a magnitude which is adequate for holding a pulled-up armature but inadequate for pulling up the armature from rest position; a first controllable semiconductor switch; a first capacitor connected in a first series circuit arrangement with the first semiconductor switch, the first seriescircuit arrangement being connected in parallel with the series connected choke and excitation winding and producing a pulse-like current amplification ,of the holding current in the excitation winding when the first semiconductor switch is controlled; a second controllable semiconductor switch, the second series circuit arrangement being connected in parallel with the excitation winding and producing a pulse-like current reduction of the holding current in the excitation winding when the second semiconductor: switch is controlled; a first voltage source for applying a first voltage to the first capacitor for maintaining the first capacitor in charged condition; and a second voltage source for applying a second voltage to the second capacitor for maintaining the second capacitor in charged condition.

2. A circuit as claimed in claim 1, further comprising a first diode poled in forward direction connected between the current supply means and the choke and a second diode poled in forward direction connected between the excitation winding and the current supply 3. A circuit as claimed in claim 1, further comprising a third diode connected in shunt with the choke and poled in inverse direction for the holding current of the excitation winding.

4. A circuit as claimed in claim 1, whereineach of the first and second semiconductor switches comprises a thyristor. I

5. A circuit'as claimed in claim 1, wherein the choke has an inductivity at least equal to the inductivity of the excitation winding.

6. A circuit as claimed in claim 1, wherein the electromagnetic switch has a magnetic circuit comprising laminated sheets.

7. A circuit as claimed in claim 4, wherein the current supply means comprises a source of voltage having a positive terminal and a negative terminal and the first on the electromagarrangement is coupled to the positive terminal of the source of voltage and the capacitor of the first series circuit arrangement is connected to the negative terminal of the source of voltage. 2

8. A circuit as claimed in claim 4, wherein the current supply means comprises a source of voltage having a positive terminal and a negative terminal and the second series circuit arrangement switches off the electromagnetic switch and the thyristor of the second series circuit arrangement is connected to the negative second semiconductorthe electromagnetic switch.

10. A circuit as claimed in claim 7, wherein the thyristor of the second series circuit arrangement has a control electrode and is controlled by a control signal supplied thereto to release the switch OFF condition of the electromagnetic switch.

t k k l 

1. A circuit for rapid excitation and de-excitation of an electromagnetic switch such as a relay, contactor, magnetic valve, and the like, by direct current, the electromagnetic switch having an excitation winding and an armature controlled in position by the excitation winding, said circuit comprising a choke connected in series with the excitation winding; current supply means coupled to the choke and the excitation winding for providing a flow of steady holding current through the excitation winding via the choke, the current having a magnitude which is adequate for holding a pulled-up armature but inadequate for pulling up the armature from rest position; a first controllable semiconductor switch; a first capacitor connected in a first series circuit arrangement with the first semiconductor switch, the first series circuit arrangement being connected in parallel with the series connected choke and excitation winding and producing a pulse-like current amplification of the holding current in the excitation winding when the first semiconductor switch is controlled; a second controllable semiconductor switch; a second capacitor connected in a second series circuit arrangement with the second semiconductor switch, the second series circuit arrangement being connected in parallel with the excitation winding and producing a pulse-like current reduction of the holding current in the excitation winding when the second semiconductor switch is controlled; a first voltage source for applying a first voltage to the first capacitor for maintaining the first capacitor in charged condition; and a second voltage source for applying a second voltage to the second capacitor for maintaining the second capacitor in charged condition.
 2. A circuit as claimed in claim 1, further comprising a first diode poled in forward direction connected between the current supply means and the choke and a second diode poled in forward direction connected between the excitation winding and the current supply means.
 3. A circuit as claimed in claim 1, further comprising a third diode connected in shunt with the choke and poled in inverse direction for the holding current of the excitation winding.
 4. A circuit as claimed in claim 1, wherein each of the first and second semiconductor switches comprises a thyristor.
 5. A circuit as claimed in claim 1, wherein the choke has an inductivity at least equal to the inductivity of the excitation winding.
 6. A circuit as claimed in claim 1, wherein the electromagnetic switch has a magnetic circuit comprising laminated sheets.
 7. A circuit as claimed in claim 4, wherein the current supply means comprises a source of voltage having a positive terminal and a negative terminal and the first series circuit arrangement switches on the electromagnetic switch and the thyristor of the first series circuit arrangement is coupled to the positive terminal of the source of voltage and the capacitor of the first series circuit arrangement is connected to the negative terminal of the source of voltage.
 8. A circuit as claimed in claim 4, wherein the current supply means comprises a source of voltage having a positive terminal and a negative terminal and the second series circuit arrangement switches off the electromagnetic switch and the thyristor of the second series circuit arrangement is connected to the negative terminal of the source of voltage and the capacitor of the second series circuit arrangement is connected to a common point in the connection between the choke and the excitation winding.
 9. A circuit as claimed in claim 7, wherein the thyristor of the first series circuit arrangement has a control electrode and is controlled by a control signal supplied thereto to release the switch ON condition of the electromagnetic switch.
 10. A circuit as claimed in claim 7, wherein the thyristor of the second series circuit arrangement has a control electrode and is controlled by a control signal supplied thereto to reLease the switch OFF condition of the electromagnetic switch. 